As people become increasingly demanding on video resolution, information transmission bandwidth and storage capacity occupied by video and image contents also become larger. How to further increase the compression ratio of a video becomes a serious challenge. Although many technologies have been proposed for improving interframe prediction, few have been proposed for improving intraframe prediction. Without interframe image references, compression efficiency cannot be effectively improved.
According to conventional intraframe prediction technologies, the current predicted block is generally obtained by extrapolation to the reconstructed pixel points on the left of and above the current block, where the pixel points on the right and beneath cannot be used as reference pixel points. Because the processing sequence of coded units in the encoder/decoder is raster scan or Z-scan, the coded unit on the right of beneath the current block cannot be reconstructed before completion of coding the current block; as such the pixel points on the right of and below the current block cannot be referenced. This greatly reduces the information that may be referenced by the intraframe prediction and hampers accuracy of intraframe prediction.